VVisual: line mode: a special handler when selection becomes a caret
VVisual: line mode: a special handler when selection becomes a caret

* now can go back to another direction
* ensure at least a line is selected
  * if the old is 1 line, then try to make the new selection have 2 lines

gdh1995/vimium-plus,gdh1995/vimium-plus,gdh1995/vimium-plus